The clever and talented Syne Mitchell suggested batching dyed cellulose in the microwave rather than letting it sit overnight, and I gave it a try with a nice fat skein of Leafy Sheep bamboo blend sock yarn. Then I did it again with two rather small skeins, and really liked the way the colors came out. All aquiver to knit up a sample with the small skeins, I looked at them again once they were completely dry.
Nice colors, eh?
Then I looked more closely.
Wot’s this, then?

Ick! At first I was thinking it might be a dye issue, or a lack of dye issue, or a soda ash issue, but then I realized that I must have melted some of the nylon fibers.  On the small skeins, it’s quite obvious.

One the large skein, it’s there, just a bit harder to find.
Only pretty from a distance

If you look at the purplish bit on the upper right, between the pink and the blue, you’ll see that the texture is a bit irregular.  And there’s more, scattered throughout.  I’d been unsure about the dye job anyway, pondering overdying it with protein dyes, but now it’s either bound for the trash, or destined to life as a Horrible Example.

Your take-away message for today:  Don’t put nylon in the microwave.

Update:  see the comments for a short discussion on this.  Microwaving yarn with nylon content can be okay if you are careful and don’t overcook it.